It has been more than 20 years since scientists discovered that mutations in the gene huntingtin cause the devastating progressive neurological condition Huntington’s disease, which involves involuntary movements, emotional disturbance, and cognitive impairment. Surprisingly little, however, has been known about the gene’s role in normal brain activity. Now, a study from The Scripps Research Institute’s (TSRI’s) Florida campus and Columbia University shows it plays a critical role in long-term memory. “We found that huntingtin expression levels are necessary for what is known as long-term synaptic plasticity—the ability of the synapses to grow and change—which is critical to the formation of long-term memory,” said TSRI Assistant Professor Sathyanarayanan V. Puthanveettil, who led the study with Nobel laureate Dr. Eric Kandel of Columbia University. In the study, published online on July 23, 2014 by the journal PLOS ONE, the team identified an equivalent of the human huntingtin protein (image)in the marine snail Aplysia, a widely used animal model in genetic studies, and found that, just like its human counterpart, the protein in Aplysia is widely expressed in neurons throughout the central nervous system. Using cellular models, the scientists studied what is known as the sensory-to-motor neuron synapse of Aplysia—in this case, gill withdrawal, a defensive move that occurs when the animal is disturbed. The study found that the expression of messenger RNAs of huntingtin—messenger RNAs are used to produce proteins from instructions coded in genes—is increased by serotonin, a neurotransmitter released during learning in Aplysia. After knocking down production of the huntingtin protein, neurons failed to function normally.
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